BBC Proms, Royal Albert Hall, London<br/>Manchester International Festival, Bridgewater Hall / Chetham's, Manchester

With Schubert to die for and a preposterous but sincere choral monolith, the Proms keeps giving its audiences a thrilling ride

Cool and suspenseful, the opening chords of Schubert's String Quintet in C Major (Prom 7) cleared the sweaty, pagan air of the Royal Albert Hall after Myung-Whun Chung's feral reading of The Rite of Spring with Orchestre Philharmonique de Radio France (Prom 6).

The first week of the BBC Proms was a roar of celebration: loud, louder, loudest. But the Belcea Quartet's performance with Valentin Erben sharpened our ears.

Thomas Mann wrote that this was music to listen to on one's deathbed. It would be a good way to go, held on the pizzicato heartbeat of the second cello, a little in love with the first cello, hero of this wordless narrative. More elastic than on the ensemble's recording, more explicit in its intimation of mortality, the Quintet seemed to sum up Schubert's strength and frailty: the Adagio a timeless kiss, the Scherzo a dance of hollow hedonism, the Hungarian-accented Allegretto a feverish act of resistance before the shattering final cadence.

One intimate masterpiece, one grand folly. Scored for two orchestras, two choruses and four brass bands, Havergal Brian's polystylistic Gothic Symphony (Prom 4) invites accusations of preposterousness. With Mahler's Eighth Symphony as his model, the self-taught Brian, who left school at 12, plundered the polychoral effects of Venice, Russian Orthodox church music and the oxygenated gasp of Tudor polyphony. The result is cluster chords, fugues, densely cultivated banks of divisi strings and a cheeky march for nine clarinets. Above all, there is sincerity: wretched horror at the slaughter of the First World War.

Performed by singers from Cardiff, Birmingham, Huddersfield, Brighton, London and Southend, with the BBC National Orchestra of Wales and the BBC Concert Orchestra, the Gothic was remarkably cohesive and expressive under Martyn Brabbins's clear, calm beat, with soprano soloist Susan Gritton gently righting the intonation of the chorus in the cruelly high tessitura of the Te Deum. But the qualities that some admire in the Gothic – its scale, its variety – are what its detractors dislike.

Brian spent eight years on the Gothic. Wagner took 27 to complete the Ring Cycle. It seems reasonable to suppose that much of that time was spent in silent labour. Commissioned as a curtain-opener for the Hallé's Manchester International Festival performance of Die Walküre, Gerard McBurney's The Madness of an Extraordinary Plan suggested an alternative scenario, in which Wagner (Roger Allam) only briefly broke off from fulminating to imagine music that – pouf! – appeared fully scored from the baton of Sir Mark Elder. Were composing this easy, anyone with a lunatic sense of their own self-importance could do it.

For those more interested in the music than the man, Madness... was a poor reason for spreading the performance over two days. Every time the Hallé played an excerpt, you wished it would continue. Its Wagner is simply beautiful, and if that burnished lyricism was more glamorous than dangerous in Act I of Die Walküre, the duet with Siegmund (Stig Andersen) and Sieglinde (Yvonne Howard) had a tenderness beyond renegade intoxication. Elder is a skilful accompanist, metering the blend to suit the timbres of his cast, seducing the most limpid, eloquent solo from cellist Nicholas Trygstad.

Susan Bullock's singing has a freshness and wit that conveys Brünnhilde's idealism and innocence – a world removed from the bitter machinations of Susan Bickley's Fricka. Clive Bayley's dour Hunding and Egils Silins's virile Wotan were compelling, the Valkyries a raucous hen party. If Katherine Broderick (Helmwige) can continue to fling out top Cs with such easy brilliance, she seems set to follow Bullock. Between Opera North and the Hallé, the M62 has become a paradise for Wagnerians.

The penultimate Manchester performance of Bach, Berio, Biber & Bartók, Béla drew a small crowd of listeners into the furtive half-light of the Quay Brothers' animations, as Alina Ibragimova played a programme of valedictory chaconnes and passacaglias for solo violin. Berio's Sequenza VIII and Bach's D minor Chaconne unfolds in counterpoint to Expressionist shadows created by strategic up-lighting. In the Biber, she disappears, her music relayed through hidden speakers. Finally, Bartók's Sonata accompanies a film that revisits many of the themes in the Quay Brothers' In Absentia (2000). As ever, Ibragimova plays with excoriating passion.

BBC Proms (845 401 5040) to Sept 10; Alina Ibragimova, Wilton's Music Hall (020 7638 8891), Mon to Wed

Next Week:

Opera Holland Park's Rigoletto takes off. Anna Picard will be there

Classical Choice

Roger Norrington gives a historically informed performance of Mahler's Ninth Symphony with the Stuttgart Radio Symphony Orchestra at the BBC Proms, Royal Albert Hall, London (Mon). Ears will be health-checked at the door as Vignette Productions' post-apocalyptic La Bohème sets Puccini's opera in the style of 28 Days Later, Village Underground, Shoreditch, (Tue and Thu), West Road Concert Hall, Cambridge (Sat).